Folding door systems, methods and devices includes a first door panel, a second door panel, and an astragal mounted to the first panel. A concealed hinge block is embedded within the astragal and provides a vertically adjustable base for a pin knuckle that couples to a receiver knuckle on the second panel. An integrated shoot bolt actuator system that drives bolts into a header and sill to secure the panels in a closed position operates around the hinge block. A worm gear-based adjuster mechanism within a receiver knuckle enables fine alignment between the two door panels in relation to the hinge knuckle. The system conceals all fasteners and actuator components within the astragal, supporting both inswing and outswing configurations. The modular architecture improves field adjustability, enhances aesthetics, and maintains compatibility with standard door panel constructions while enabling the panels to fold fully open against one another for maximum clear opening.